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Exposure apparatus and method of manufacturing device

Exposure apparatus and method of manufacturing device description/claims

1. Field of the Invention

The present invention relates to an exposure apparatus and a method of manufacturing a device.

2. Description of the Related Art

When a semiconductor device, a liquid crystal display device, a thin-film magnetic head, or the like is to be manufactured in a lithography process, a semiconductor exposure apparatus is used, which forms a latent image on a photoresist coated on a substrate by projecting a circuit pattern on a reticle via a projection optical system.

With a decrease in the size of the circuit patterns of devices and an increase in packing density, a projection exposure apparatus for semiconductor manufacture is required to transfer patterns on reticles at high resolutions. A resolution is based on the numerical aperture (NA) of a projection optical system and the wavelength of exposure light. That is, the resolution increases as the NA increases and the wavelength of exposure light decreases.

With regard to the shortening of wavelengths, a technique of shortening the wavelength of light generated by a light source has been studied. With this study, the wavelength of exposure light tends to decrease from 248 nm, which is the oscillation wavelength of a KrF excimer laser, to 193 nm, which is the oscillation wavelength of an ArF excimer laser.

With regard to an increase in numerical aperture (NA), a projection exposure technique using an immersion method has attracted a great deal of attention. The immersion method has originally been proposed to increase the resolution of an optical microscope. According to this technique, the space between a lens and a sample is filled with a liquid having a refractive index greater than 1.

WO99/49504 has proposed an exposure apparatus using this immersion method, i.e., an immersion exposure apparatus.

Consider a case in which the gap between the final optical element of a projection optical system and a substrate is filled with ultrapure water having a refractive index of 1.44 as a liquid. Assuming that the maximum incident angle of light on a wafer remains unchanged, the NA obtained when a light beam passes through ultrapure water is 1.44 times that obtained when the gap is filled with a gas. According to the Rayleigh equation, the resolution increases by 1.44 times. This makes it possible to obtain a resolution of NA>1.

In an immersion exposure apparatus, the photoresist coated on a substrate comes into contact with the liquid, and hence causes a reaction with the liquid. This may change the characteristics of the photoresist. That is, the chemical characteristics of the photoresist with respect to a developing solution may change depending on the contact time with the liquid. It is therefore possible that the line width of a latent image pattern formed on the photoresist, i.e., the CD (Critical Dimension), will vary.

For example, the immersion method uses an ArF laser as a light source, and also uses a chemically amplified resist as a photoresist. When exposure light is applied to a chemically amplified resist, the resist produces an acid. The produced acid is heated and acts as a catalyst which causes many chemical reactions. This catalytic reaction changes the solubility of a chemically amplified resist with respect to the developing solution. This makes it possible to form a pattern. At this time, if the liquid which is made to come into contact with the photoresist contains a component which deactivates the acid, e.g., ammonia, the acid produced by the photoresist upon exposure to light is deactivated, resulting in loss of solubility with respect to the developing solution. As a result, the line width of an obtained pattern may vary depending on the contact times of the photoresist with the liquid.

For example, in the immersion method, the photoresist which comes into contact with the liquid sometimes absorbs the liquid. As a result, the sensitivity of the photoresist with respect to the amount of exposure light varies. It is therefore possible that the line width of an obtained pattern will vary depending on the contact time of the photoresist with the liquid.

In order to solve these problems, resist makers have developed top coats to be coated as passivation films on resists. However, a liquid may pass through a top coat, and a complicated step is required to remove the top coat in developing operation, resulting in an increase in cost. For these reasons, it is required to use only a conventional photoresist without using any top coat.

The present invention provides for reducing variation in a line width of a pattern.

According to first aspect of the present invention, an exposure apparatus which includes a projection optical system configured to project light from an original onto a substrate and performs an exposure of the substrate to light via a liquid that fills a gap between a final optical element of the projection optical system and the substrate, the apparatus comprises a controller configured so that 1) an exposure condition for the substrate is input to the controller, the exposure condition including a shot area layout and a dose for a shot area, and 2) the controller obtains a contact time during which the shot area is to be kept in contact with the liquid based on the input exposure condition, and corrects the input dose based on the obtained contact time.

According to a second aspect of the present invention, a method of manufacturing a device comprises: exposing a substrate to light using the exposure apparatus according to the first aspect of the present invention; developing the exposed substrate; and processing the developed substrate to manufacture the device.

According to the present invention, variation in a line width of a pattern can be reduced.

Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

• Provisional Patent
• Utility Patent

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